A control valve of this type corresponds in terms of its construction to the known control valves of Wabco Series No. 461315xx which is shown in FIG. 1 in a longitudinal section. In the case of this control valve, the first valve piston is guided in a housing upper part and is sealed by means of an O-ring seal. A plunger piston which can be actuated manually or with the aid of an actuator acts via a pressure plate and an elastomer spring element on the first valve piston which for its part interacts in a known way with a first valve system, to which it belongs. Since, in the case of an actuation of the control valve, a push rod (not shown) acts on the plunger piston with an angular deviation which changes upon actuation with regard to the longitudinal axis of the control valve, lateral forces and tilting moments are transmitted via the pressure plate on the valve piston. In order to absorb these loads, the first valve piston is guided in the housing upper part by way of a cylindrical guide sleeve which has a comparatively large axial length, as a result of which the installation space which is required for it in the housing upper part is rather long. Furthermore, tilting moments and transverse forces which act on the plunger piston are transmitted via the pressure plate directly to the cylindrical guide of the valve piston and, under unfavourable operating conditions, can lead to an undesired reduction of the sealing action of the O-ring seal on account of the increased wear which is brought about by the transverse forces and the tilting moments. For this reason, this known control valve which has proven itself satisfactorily in normal operation needs to be improved.
Against this background, the invention is based on the object of improving a pneumatic control valve of the type mentioned at the outset, in such a way that the sealing action of the valve piston with respect to the housing upper part is impaired less by tilting moments and transverse forces which occur upon actuation of the control valve. Moreover, the novel control valve is to be comparatively simple to assemble and to have a comparatively low weight.